EP2034614B1 - Syntoniseur FM - Google Patents

Syntoniseur FM Download PDF

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Publication number
EP2034614B1
EP2034614B1 EP08015656A EP08015656A EP2034614B1 EP 2034614 B1 EP2034614 B1 EP 2034614B1 EP 08015656 A EP08015656 A EP 08015656A EP 08015656 A EP08015656 A EP 08015656A EP 2034614 B1 EP2034614 B1 EP 2034614B1
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EP
European Patent Office
Prior art keywords
signal
circuit
frequency
band
adjacent
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EP08015656A
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German (de)
English (en)
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EP2034614A3 (fr
EP2034614A2 (fr
Inventor
Keiji Kobayashi
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Sanyo Electric Co Ltd
System Solutions Co Ltd
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Sanyo Electric Co Ltd
Sanyo Semiconductor Co Ltd
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Publication of EP2034614A3 publication Critical patent/EP2034614A3/fr
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/06—Receivers
    • H04B1/10—Means associated with receiver for limiting or suppressing noise or interference
    • H04B1/1027—Means associated with receiver for limiting or suppressing noise or interference assessing signal quality or detecting noise/interference for the received signal
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03J—TUNING RESONANT CIRCUITS; SELECTING RESONANT CIRCUITS
    • H03J1/00—Details of adjusting, driving, indicating, or mechanical control arrangements for resonant circuits in general
    • H03J1/0008—Details of adjusting, driving, indicating, or mechanical control arrangements for resonant circuits in general using a central processing unit, e.g. a microprocessor
    • H03J1/0058—Details of adjusting, driving, indicating, or mechanical control arrangements for resonant circuits in general using a central processing unit, e.g. a microprocessor provided with channel identification means

Definitions

  • the present invention relates to an FM tuner for receiving frequency-modulated (FM) signals.
  • FM signals With FM signals, the frequency of a carrier wave is changed on the basis of an audio signal or the like; therefore, a frequency bandwidth that is wider than for, e.g., AM signals, is required when they are transmitted. Accordingly, when an FM tuner receives a desired transmission signal, the tuner is readily subjected to interference from other signals transmitted at frequencies that are close to the frequency of the desired transmission signal (adjacent interference). Adjacent interference is capable of adversely affecting the quality of the audio signals detected from the reception signals. Specifically, adjacent interference occurs in a case where another station exists on a frequency that is close to that of the station the listener desires.
  • the quality of the audio output reproduced by the FM tuner will also deteriorate in a multipath reception state, in which waves directly received from a radio broadcasting station are received along with waves reflected by buildings or other objects along the transmission path (multipath interference state).
  • Adjacent interference and multipath interference are undesirable in radio data systems (RDS) wherein text data or the like is superimposed on an FM radio broadcast signal and transmitted.
  • FIG. 4 is a block diagram showing a configuration of a conventional FM tuner.
  • An RF (radio frequency) signal received by an antenna 2 is frequency-converted to a first intermediate signal S IF1 having a first intermediate frequency (IF) f IF1
  • the S IF1 is frequency-converted to a second intermediate signal S IF2 having a second intermediate frequency f IF2
  • the S IF2 is input to an IFBPF 4.
  • the IFBPF 4 is a bandpass filter having a frequency f IF2 as a center frequency.
  • a bandwidth W F of the filter can vary within a range of, e.g., about 40 kHz to about 220 kHz.
  • An FM signal that has passed through the IFBPF 4 is inputted to an FM detection circuit 8 via a limiter amp 6.
  • the FM detection circuit 8 FM-detects an output signal of the limiter amp 6, and outputs a detection signal S DET .
  • An S-meter circuit 10 receives the first intermediate signal S IF1 , generates a signal S M-AC that corresponds to an amplitude variation component included in the inputted signal, and then smoothes the variation component using a low-pass filter (LPF) and generates a reception field strength signal S M-DC . Included in the variation component signal S M-AC is a component that corresponds to adjacent interference and multipath interference.
  • LPF low-pass filter
  • a high-pass filter (HPF) 12, a detection circuit 14, and a comparator 16 are provided as circuits for detecting the presence or absence of adjacent interference and multipath interference on the basis of S M-AC .
  • the HPF 12 is capable of switching the cut-off frequency f c according to whether one or the other of a frequency band component corresponding to adjacent interference or a frequency band component corresponding to multipath interference is extracted from S M-AC .
  • the detection circuit 14 detects the high-frequency component having passed through the HPF 12, and performs a conversion to DC voltage V SQ .
  • the comparator 16 compares an output level V SQ of the detection circuit 14 with a reference voltage V ref1 set to a predetermined threshold value.
  • V SQ a predetermined voltage V H (H level) corresponding to a logical value of "1" is output as an SQ sensor signal S SQ indicating a determination result that either adjacent interference or multipath interference has occurred.
  • V SQ ⁇ V ref1 a predetermined voltage V L (L level, V L ⁇ V H ) corresponding to a logical value of "0" is output as S SQ indicating a determination result that neither adjacent interference nor multipath interference has occurred.
  • an AF search is performed for automatically selecting a broadcasting station with favorable reception conditions. For example, S SQ is utilized in assessing the reception state when automatic channel selection is performed.
  • a circuit composed of an HPF 18 and a detection circuit 20 may be provided as another circuit for detecting adjacent interference.
  • This circuit outputs a DC signal S AI of a voltage level that corresponds to the strength of a high-frequency component that can be generated by adjacent interference.
  • the cut-off frequency f C of the HPF 18 may be approximately 100 kHz.
  • the V SQ or S AI corresponding to an adjacent interference component is used in a bandwidth control circuit 22 for controlling a bandwidth W F of the IFBPF 4.
  • the bandwidth control circuit 22 narrows W F in instances in which adjacent interference has occurred, and reduces the effect of adjacent interference on the output audio signal.
  • the detection circuits 14, 20 perform the detecting using CR-assisted smoothing, and the detection outputs V SQ , S AI accordingly provide a predetermined time constant. In a case where the V SQ or S AI is used to control of the bandwidth W F of the IFBPF 4, the time constants will have the effect of minimizing the effect on the output acoustic signal caused by W F being frequently switched between high and low.
  • a comparator 24, an SD band judgment circuit 26, and an SD circuit 28 are provided as circuits for detecting a broadcasting station when the aforedescribed AF search or another type of automatic station selection is performed.
  • SD denotes "station detection”.
  • the comparator 24 compares the reception field strength signal S M-DC received from the S meter circuit 10, and a reference voltage V ref2 set to a predetermined threshold value; and emits an H level output to the SD circuit 28 if S M-DC ⁇ V ref2 , or an L level output if S M-DC ⁇ V ref2 .
  • the FM detection circuit 8 detects the output signal of the limiter amplifier 6, and generates S DET .
  • S DET is fed to a stereo demodulating circuit (not shown).
  • the stereo demodulating circuit demodulates the detection signal to an audio signal composed of an R channel signal and an L channel signal.
  • the audio signal is fed to output terminals of a speaker or the like.
  • a f-V conversion ("S curve") characteristic exists between a frequency f of the intermediate signal S IF2 received by the FM detection circuit 8 and a detection output voltage V.
  • the SD band judgment circuit 26 uses the f-V conversion characteristic, and, based on a null voltage ⁇ V generated from the detection signal S DET produced by the FM detection circuit 8, determines whether the band of the reception station lies within the target band (SD band).
  • the null voltage ⁇ V is a signal that corresponds to the difference between an AFC voltage V AFC and a reference voltage V ref3 , with V AFC being generated once the detection output S DET of the FM detection circuit 8 has been smoothed by a capacitor C AFC that is earthed on one terminal.
  • a resistor R AFC that acts as a load on the V AFC connects the V AFC and the reference voltage V ref3 , and the voltage generated between the terminals of the R AFC enters the SD band judgment circuit 26 as ⁇ V.
  • FIG. 5 is a graph that schematically depicts the f-V conversion characteristic, with the horizontal axis showing the frequency f, and the vertical axis showing the null voltage ⁇ V.
  • the SD band has the intermediate frequency at its center, and is set to a predetermined width to avoid being adversely affected by signals from adjacent channels.
  • the SD band judgment circuit 26 is configured using a window comparator, and is set so that the window is a voltage range associated with the SD band in accordance with the f-V conversion characteristic. In a case where the null voltage ⁇ V lies within the window, the SD band judgment circuit 26 outputs an H-level SD band judgment signal to the SD circuit 28.
  • the SD circuit 28 outputs the logical product (AND) of the outputs of the comparator 24 and the SD band judgment circuit 26 as an SD signal S SD .
  • the SD signal indicates whether the reception station has been detected at the tuning frequency set during automatic station selection. In a case where a reception signal of a predetermined strength is obtained in the SD band, the SD circuit 28 outputs an H level that shows that the reception station has been detected.
  • an AF search is performed and a broadcasting station having a favorable reception state is automatically selected in order to receive an FM broadcast when the signal quality is consistently good, or in cases where reception is poor.
  • the AF search is preferably performed at as high a speed as possible.
  • quickly detecting the reception state is not the only important criterion when an AF search is performed; the accuracy with which the detection is performed must also be taken into consideration.
  • European RDS receivers in particular use only one channel in order to keep costs low.
  • means is required for moving the reception channel to another broadcast channel for a limited period of time; and then accurately detecting adjacent interference while performing PLL locking, detecting stations, detecting adjacent interference, detecting multipath interference, and performing other processes.
  • Document EP A 0 430 469 describes a signal quality detecting circuit for an FM receiver, wherein the receiver includes an IF detector generating an intensity signal indicating the received field strength of the FM signal being received and a FM demodulator generating an automatic frequency control signal indicating a frequency error at which the FM signal is received.
  • the signal quality detecting circuit comprises a level detector means adapted to be coupled to the IF detector for producing a first signal when the intensity signal is greater than a predetermined intensity, a window detector means adapted to be coupled to the FM demodulator for producing a second signal when the automatic frequency control signal is within a predetermined window, a noise filter means adapted to be coupled to the IF detector for generating a filtered noise signal derived from the intensity signal, wherein the filter means rejects frequencies containing components related to the intelligence contained in the FM signal, a peak detector means coupled to the noise filter means for producing a third signal when the filtered noise signal is below a predetermined peak value, and a logic means coupled to the level detector means, the window detector means and the peak detector means for producing an indicating signal in response to the simultaneous occurrence of the first, second and third signals to indicate that a high quality FM signal is received.
  • Document JP 09 046184 A describes an automatic channel selection device.
  • An AMIF signal output from an IF filter is amplified by a limiter amplifier and FM-detected by an FM detector and converted into a DC output voltage and it is decided by an IF detuning detection section whether or not the voltage is within a prescribed voltage range.
  • the IF detuning detection section provides an output of a high level to an AND gate only when the DC voltage from the FM detector is within a prescribed voltage range.
  • the intensity of the AMIF signal is detected by an intermediate frequency signal intensity detection section in response to an AGC voltage of an AGC amplifier.
  • the intermediate frequency signal intensity detection section provides an output of a high level to the AND gate when the AGC voltage is a prescribed voltage or exceeding it.
  • the AND gate receives two high level signals, that is, when the frequency of the IF signal is within a prescribed range and the signal is a prescribed signal intensity or exceeding it, it provides an output of a high level.
  • Document US 2005/101273 A1 describes an audio broadcast receiver and automatic broadcasting-station selecting method. While a plurality of seek object frequencies decided in advance is set as a receiving frequency in order, seek object frequencies meeting at least the following conditions are selected.
  • the electric field strength of a seek object frequency being currently received must exceed a predetermined threshold value.
  • the second intermediate-frequency signal of the seek object frequency being received must be in a prescribed frequency band.
  • the absolute value of the difference between the electric field strength of the neighbouring seek object frequency whose electric field strength exceeds the predetermined threshold value and the electric field strength of the seek object frequency being received must not exceed another threshold value.
  • the modulation factor of the seek object frequency being received must not exceed a further threshold value.
  • the present invention was contrived in order to overcome the problems described above, and it is an object thereof to provide an FM tuner that enables adjacent interference to be detected with improved accuracy.
  • the FM tuner of the present invention comprises: an intermediate signal generating circuit for subjecting a reception signal to a frequency conversion wherein a carrier frequency of a desired reception FM signal is shifted to a predetermined intermediate frequency, and generating an intermediate signal; a detection circuit for detecting the intermediate signal, and generating a detection signal having a voltage value corresponding to an amount of frequency deviation; a band judgment circuit for generating a band judgment signal in relation to whether or not the detection signal is within a target voltage range that is set according to the band of the desired reception FM signal; a strength signal generating circuit for generating a field strength signal corresponding to a field strength of the reception signal; a strength judgment circuit for generating a strength judgment signal in relation to whether or not the field strength signal is equal to or higher than a predetermined reference strength; and a station detecting circuit for determining the presence or absence of the desired reception FM signal based on the strength judgment signal and the band judgment signal, and outputting a station detecting signal; wherein the station detecting circuit further determines the presence or absence
  • FIG. 1 is a schematic block diagram of an FM tuner according to the present embodiment.
  • An FM tuner 50 is formed on a common circuit board with the main components thereof designed as integrated circuits, and is substantially configured as an integrated tuner module.
  • the module is incorporated as one component of an onboard audio device in an automotive vehicle, for example.
  • An RF signal S RF received by an antenna 54 is inputted into a signal processing system in the FM tuner 50.
  • the system comprises an FM-RF tuned amplifier circuit 56; a first local oscillation unit 58; a first mixing circuit 60; bandpass filters (BPF) 62, 66; buffer amps 64, 72; a second local oscillation unit 68; a second mixing circuit 70; an IFBPF 74; a limiter amplifier 76; an FM detection circuit 78; a noise canceler 80; and a matrix circuit (MPX circuit) 82.
  • the signal processing system generates an output signal S OUT corresponding to the audio signal of the desired station from the RF signal S RF .
  • the FM tuner 50 includes a quartz crystal oscillation circuit 90, an S-meter circuit 92, a bandwidth control circuit 94, a quality sensor circuit 96, an adjacent interference noise extraction circuit 98, a modulation degree signal generating circuit 100, a receiving field strength-judgment circuit 102, an SD band judgment circuit 104, and an SD circuit 106.
  • the FM tuner 50 is connected to a system bus (not shown), and operates under the control of a microcomputer or other control unit (not shown) via the system bus.
  • the RF signal S RF is inputted to the FM-RF tuned amplifier circuit 56.
  • the FM-RF tuned amplifier circuit 56 attenuates the components among the RF signal S RF that fall outside a band corresponding to a carrier wave frequency f R for the desired reception FM signal.
  • the RF signal S RF in the band that includes the frequency f R for a station that a listener wishes to receive is, thereby, passed through the FM-RF tuned amplifier circuit 56.
  • the signal outputted from the FM-RF tuned amplifier circuit 56 is inputted to the first mixing circuit 60.
  • the first local oscillation unit 58 has a first oscillator circuit 110 and a frequency dividing circuit 112.
  • the first oscillator circuit 110 has a PLL circuit that uses an original oscillation signal So output by the quartz crystal oscillation circuit 90 as a reference oscillation signal.
  • the PLL circuit outputs an oscillation signal S OSC1 having a frequency f OSC1 corresponding to the station that the listener wishes to receive.
  • the f OSC1 is controlled by a controller in the first oscillator circuit 110.
  • the f OSC1 is set to ⁇ (f R + f IF1 ) or ⁇ (f R - f IF1 ), where ⁇ is the division ratio of the frequency division circuit 112.
  • the division circuit 112 divides S OSC1 from the first oscillation circuit 110 by ⁇ , generates S LO1 , and sends an output to the first mixing circuit 60.
  • the first mixing circuit 60 mixes the inputted RF signal S RF with the first local oscillation signal S LO1 inputted from the first local oscillation unit 58, and generates a first intermediate signal S IF1 .
  • a frequency f LO1 of S LO1 is adjusted to be converted to a predetermined first intermediate frequency f IF1 in a frequency conversion of the signal for the desired station having a frequency f R and included in S RF to the S IF1 outputted by the first mixing circuit 60.
  • the first intermediate frequency f IF1 is set, for example, to 10.7 MHz.
  • S IF1 is inputted to the second mixing circuit 70 via the BPF 62, the buffer amp 64, and the BPF 66.
  • the BPFs 62, 66 may be configured using, e.g., a ceramic filter.
  • the second local oscillation unit 68 In response to a case where f IF1 is set to 10.7 MHz and f IF2 is set to 450 kHz, the second local oscillation unit 68 generates an S LO2 with a frequency f LO2 of 10.25 MHz.
  • the second local oscillation unit 68 of the present embodiment has a frequency division circuit 114 in order to generate S LO2 .
  • the frequency division circuit 114 divides by 2 the oscillation signal So that is outputted by the quartz crystal oscillation circuit 90 and has a frequency of, e.g., 20.5 MHz; generates S LO2 , and feeds the signal to the second mixing circuit 70.
  • the second mixing circuit 70 mixes the first intermediate signal S IF1 input from the BPF 66 with the second local oscillation signal S LO2 input from the second local oscillation unit 68, and generates a second intermediate signal S IF2 having a second intermediate frequency f IF2 .
  • the frequency f LO2 of S LO2 is set to (f IF1 - f IF2 ), and the desired reception signal having frequency f IF1 and included in S IF1 is converted to frequency f IF2 in the second mixing circuit 70.
  • the second intermediate frequency f IF2 is set, for example, to 450 kHz.
  • the IFBPF 74 is a bandpass filter that uses f IF2 as the center frequency and is capable of variably setting the pass bandwidth W F .
  • the pass bandwidth W F of the IFBPF 74 is controlled by the bandwidth control circuit 94, as will be discussed hereafter.
  • the limiter amplifier 76 increases the amplitude of the FM signal and creates a rectangular wave. As a result, the AM modulation component superimposed on the FM signal due to multipath interference or another reason can be eliminated, and any deterioration in the demodulation S/N originating from AM modulation will be prevented.
  • the FM signal that has been amplified by the limiter amplifier 76 and turned into a rectangular wave is inputted to the FM detection circuit 78.
  • the FM detection circuit 78 is composed of, e.g., a quadrature detection circuit.
  • the FM detection circuit 78 performs FM detection of S IF2 that has been inputted from the limiter amplifier 76, and outputs a detection output signal S DET .
  • the main format used for an FM detection circuit 78 has been one in which quadrature detection or PLL detection is used, and not an LC tuned circuit.
  • One characteristic of such formats is the wide bandwidth of the f-V conversion characteristic.
  • the f-V conversion characteristic may be used within a range of approximately ⁇ 200 kHz for the central frequency f IF2 of the intermediate signal S IF2 that is inputted to the FM detection circuit 78.
  • the noise canceler 80 removes pulse noise from the detection output signal S DET .
  • the reception signal can be superimposed with noise in the form of pulses, having a short time width and a high amplitude, as caused by the operation of the vehicle engine, power-assisted mirrors, windshield wipers, or other components.
  • the noise canceler 80 minimizes any deterioration in sound quality caused by pulse noise.
  • the matrix circuit 82 uses a pilot signal inputted from a pilot signal extraction circuit (not shown) to cancel out a pilot signal from S DET , and is able extract the (L+R) signal and the (L-R) signal, respectively.
  • the matrix circuit 82 can separate the L signal and the R signal from the (L+R) signal and the (L-R) signal and output them.
  • the S-meter circuit 92 generates a signal S M-AC corresponding to the variation component included in S IF1 on the basis of, e.g., S IF1 inputted from the BPF 66; smoothes the variation component using the LPF; and generates the reception field strength signal S M-DC .
  • S M-DC is inputted to the receiving field strength judgment circuit 102 and the bandwidth control circuit 94. These components shall be described hereunder.
  • the quality sensor circuit 96 is a circuit that detects the presence of adjacent interference or multipath interference based on S M-AC , and comprises an HPF 130, a detection circuit 132, and a comparator 134.
  • the HPF 130 is capable of switching the cut-off frequency f C according to whether one or the other of a frequency band component corresponding to adjacent interference or a frequency band component corresponding to multipath interference is extracted from S M-AC .
  • adjacent interference if ⁇ f is used as the RF frequency differential between the broadcast station causing adjacent interference and the desired station, a high-frequency component having a frequency corresponding to ⁇ f will appear in S M-AC when adjacent interference occurs.
  • the cut-off frequency f C of the HPF 130 when the component corresponding to the adjacent interference is extracted from S M - AC can be, e.g., approximately 100 kHz.
  • the frequency of high-frequency components caused by multipath interference are typically not as high as the component caused by adjacent interference, the f C when the component corresponding to multipath interference are extracted from S M-AC can be set to approximately 50 kHz.
  • the detection circuit 132 rectifies and detects the high-frequency components passing through the HPF 130, and generates a DC signal V SQ of a voltage level that corresponds to the amount of adjacent interference noise components or multipath noise.
  • the V SQ is used to switch the passing bandwidth W F of the IFBPF 74 between high and low in the bandwidth control circuit 94, as described hereunder.
  • the V SQ is smoothed using a predetermined time constant.
  • the comparator 134 compares an output level V SQ of the detection circuit 132 with a reference voltage V ref1 set to a predetermined threshold value. For example, if V SQ > V ref1 , the comparator 134 outputs an H level as an SQ sensor signal S SQ indicating a determination result that adjacent interference or multipath interference has occurred. However, if V SQ ⁇ V ref1 , the comparator 134 outputs an L level as S SQ indicating a determination result that neither adjacent interference nor multipath interference have occurred.
  • the adjacent interference noise extraction circuit 98 is provided as a separate circuit for detecting adjacent interference.
  • the adjacent interference noise extraction circuit 98 extracts adjacent interference noise components included in the output signal S DET of the FM detection circuit 78.
  • the signal S DET that is generated when adjacent interference occurs has not only a signal component of an audio band corresponding to the desired station but also a high-frequency component having a frequency corresponding to the RF frequency differential ⁇ f between the desired station and the interfering station.
  • the adjacent interference noise extraction circuit 98 has a HPF 138 and a detection circuit 140; and outputs a DC signal S AI1 of a voltage level that corresponds to the strength of the high-frequency components that can be generated by adjacent interference.
  • the cut-off frequency f C for the HPF 138 can be set to about 100 kHz, as with the HPF 130.
  • S AI1 is inputted to the bandwidth control circuit 94.
  • the modulation degree signal generation circuit 100 generates a DC signal S MD of a voltage level corresponding to the degree of modulation of the reception signal on the basis of S DET .
  • the modulation degree signal generation circuit 100 is composed of an LPF 142 and a detection circuit 144. The circuit removes the high-frequency component caused by adjacent interference or the like, and outputs the DC signal S MD of a voltage level corresponding to the degree of modulation. S MD is used by the bandwidth control circuit 94.
  • the bandwidth control circuit 94 controls the bandwidth W F of the IFBPF 74 on the basis of S M-DC generated by the S-meter circuit 92, the V SQ generated in the quality sensor circuit 96, S AI1 generated by the adjacent interference noise extraction circuit 98, and S MD outputted from the modulation degree signal generation circuit 100. For example, the bandwidth control circuit 94 determines whether or not the adjacent interference strength has exceeded a predetermined threshold value on the basis of V SQ and S AI1 ; and, if the strength is equal to or less than the threshold value, the bandwidth control circuit 94 sets the W F to a standard bandwidth that is relatively wide so audio distortion will not occur.
  • the bandwidth control circuit 94 determines that adjacent interference has occurred, and makes the W F narrower than the standard bandwidth. As a result, it is possible to remove the adjacent interference wave in the IFBPF 74.
  • the bandwidth control circuit 94 will make the bandwidth W F narrower even if, e.g., the adjacent interference strength is at or below a predetermined threshold value. As a result, treble component noise that increases in a weak field state is removed by the IFBPF 74, and sensitivity is improved. In the case of a high degree of modulation, audio distortion will readily occur if W F is narrowed.
  • the bandwidth control circuit 94 sets the W F to the standard bandwidth, even in a weak field state, provided that adjacent interference does not occur. However, in a state in which adjacent interference does occur, the eliminating of adjacent interference is prioritized over the preventing of audio distortion, and W F is narrowed, even at a high degree of modulation.
  • the FM tuner 50 supports RDS, and has a circuit for detecting a broadcasting station during automatic station selection.
  • the circuit comprises the receiving field strength judgment circuit 102, the SD band judgment circuit 104, and the SD circuit 106.
  • the circuit is characterized not only by functioning to detect stations as has typically been performed in the past, but also by functioning as adjacent interference detecting means for enabling high-speed AF searching under RDS.
  • the receiving field strength judgment circuit 102 determines whether the received-signal electrical field strength at the tuning frequency that has been set during automatic station selection is of an adequate level.
  • the receiving field strength judgment circuit 102 determines the result based on S M-DC , which is output by the S-meter circuit 92.
  • the receiving field strength judgment circuit 102 comprises, e.g., a comparator 150 and a voltage source 152 for feeding a reference voltage V ref2 .
  • V ref2 is set to a predetermined threshold value.
  • the comparator 150 compares S M-DC with V ref2 and outputs a receiving strength judgment signal S RE .
  • the comparator 150 outputs an H level as a signal S RE indicating a determination result that the receiving field strength is of an adequate level. However, if S M-DC ⁇ V ref2 , the comparator 150 outputs an L level as a signal S RE indicating a determination result that the receiving field strength is not of an adequate level.
  • the receiving strength judgment signal S RE is input to the SD circuit 106.
  • the SD band judgment circuit 104 is a circuit for determining whether the band of a received station lies within a predetermined frequency range W BD , based on the null voltage ⁇ V generated from the detection signal S DET , which is itself generated by the FM detection circuit 78.
  • the SD band judgment circuit 104 is configured using a window comparator.
  • FIG. 2 is a schematic circuit structure diagram showing an example of a window comparator 154 that constitutes the SD band judgment circuit 104.
  • the window comparator 154 has, as a window, a voltage range [V ref-D , V ref-U ] corresponding to the frequency range W BD on the f-V conversion characteristic.
  • an SD band judgment signal S BD having an H level is output to the SD circuit 106, whereas if ⁇ V lies outside the window, S BD having an L level is output to the SD circuit 106.
  • the window comparator 154 comprises a comparator 160, 161; an AND circuit 162; a digital-to-analog conversion circuit (DAC) 164, 165; and a register 166, 167.
  • DAC digital-to-analog conversion circuit
  • ⁇ V is input to the (-) terminal of the comparator 160; and the reference voltage V ref-U , which is the upper limit of the window, is input from the DAC 164 to the (+) terminal.
  • ⁇ V is input to the (+) terminal of the comparator 161; and reference voltage V ref-D , which is the lower limit of the window, is input from the DAC 165 to the (-) terminal.
  • the outputs of the comparators 160, 161 will both be H level, and the AND circuit 162 will output an H level as S BD .
  • the DACs 164, 165 generate a voltage corresponding to data set respectively in the registers 166, 167.
  • the registers 166, 167 are connected to a control section 170 of a microcomputer or the like via a system bus 168.
  • the control section 170 rewrites the reference voltage data stored in the registers 166, 167, thereby allowing the size of the frequency range W BD relating to the determining of the band to be changed.
  • the SD band judgment circuit 104 performs a determination based on two types of W BD ; one for when W BD is a narrow band W N , and one for when W BD is a wide band W W .
  • the SD band judgment circuit 104 comprises, e.g., two window comparators 154, enabling a configuration wherein one comparator performs a band determination for when W BD is a narrow band W N , and the other comparator performs a band determination for when W BD is a wide band W W .
  • the narrow band W N is centered on the second intermediate frequency f IF2 and is set so that, e.g., signals of adjacent channels will cause no adverse effect.
  • the wide band W W is centered on the second intermediate frequency f IF2 and is set to be greater than W N ; i.e., so that a part will include W N .
  • the wide band W W is set to a width that will include adjacent channels.
  • the control section 170 can set W N to approximately f IF2 ⁇ 50 kHz and W W to approximately f IF2 ⁇ 200 kHz in compliance with FM broadcasts within Japan.
  • the SD band judgment circuit 104 comprises only one window comparator 154, and can have a simple construction wherein the control section 170 alternatingly switches W BD between the narrow band W N and the wide band W W .
  • the SD circuit 106 generates an SD signal S SD , which indicates whether or not the desired broadcasting station has been detected at the tuning frequency set during automatic station selection; and an adjacent interference judgment signal S AI2 , which expresses whether adjacent interference is present.
  • the SD circuit 106 generates these signals based on a value D RE of S RE , which is outputted from the receiving field strength judgment circuit 102; and values D BD-N of S BD corresponding to W N and D BD-W of S BD corresponding to W W , with S BD being obtained from the SD band judgment circuit 104.
  • the SD circuit 106 determines that the desired reception station has been detected, and outputs an H level as S SD .
  • S SD can be generated by an AND circuit into which S RE and S BD corresponding to W N have been inputted.
  • FIG. 3 is a descriptive diagram showing an example of S AI2 , which is generated by the SD circuit 106.
  • the SD circuit 106 determines the value of S AI2 based on D BD-N and D BD-W , and FIG. 3 shows whether S AI2 has been set to the H level state or the L level state.
  • D BD-N H
  • a reception signal of the desired broadcasting station is present.
  • the SD circuit 106 will determine that no adverse effects are occurring as a result of interference from the adjacent station, and will output an H level as S AI2 .
  • D BD-N H
  • D BD-W H
  • the SD circuit 106 will determine that interference from an adjacent station is present, and will output an L level as S AI2 .
  • the detecting of adjacent interference using the SD circuit 106 which is provided in order to generate the SD signal S SD , tends not to be affected by variation in AC components and other such occurrences. Therefore, adjacent interference can be detected in a highly accurate manner.
  • the SD band judgment circuit 104 which has two window comparators 154, is able to obtain D BD-N and D BD-W in parallel; therefore, the presence or absence of adjacent interference can be rapidly determined. Furthermore, the control section 170 does not have to perform a process wherein a command for switching the bandwidth W BD is executed and the registers 166, 167 are rewritten on the SD band judgment circuit 104. Specifically, the switching process load is obviated, allowing time to be reduced and the control streamlined.
  • a configuration may be used wherein the two window comparators 154 output D BD-N and D BD-W to an external microcomputer or other device, whereupon the microcomputer performs the decisions in regard to the aforedescribed combinations of D BD-N and D BD-W , and detects the SD.
  • Outputting of D BD-N and D BD-W to the microcomputer or other device as performed in such instances can be accomplished using a port that doubles as another sensor output or the like.
  • the SD band judgment circuit 104 for performing a determination only for the narrow band W N .
  • the method of the present invention for detecting adjacent interference may also be used to detect adjacent interference in reception performed in non-RDS-supporting FM tuners or reception in normal circumstances.
  • a configuration may be adopted wherein adjacent interference is detected by the present invention during reception, and an AF search is initiated in a case where adjacent interference is determined to be present.
  • S AI2 to control the bandwidth W F of the IFBPF 74 instead of V SQ , which is generated in the quality sensor circuit 96, or S AI1 , which is generated by the adjacent interference noise extraction circuit 98.
  • the presence or absence of a reception signal in a frequency range corresponding to a band of a desired reception FM signal is determined based on an FM detection output using an f-V conversion characteristic.
  • the presence or absence of adjacent interference is determined on the basis of the associated results.
  • a null voltage ⁇ V used for the determination is not readily affected by AC component variation or other factors, allowing adjacent interference to be accurately detected.

Landscapes

  • Engineering & Computer Science (AREA)
  • Computer Hardware Design (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Circuits Of Receivers In General (AREA)
  • Noise Elimination (AREA)
  • Monitoring And Testing Of Transmission In General (AREA)
  • Channel Selection Circuits, Automatic Tuning Circuits (AREA)
  • Superheterodyne Receivers (AREA)

Claims (4)

  1. Syntoniseur FM (50) comprenant :
    un circuit de génération de signal intermédiaire pour soumettre un signal de réception à une conversion de fréquence où une fréquence porteuse d'un signal FM de réception souhaité est décalée vers une fréquence intermédiaire prédéterminée, et générer un signal intermédiaire ;
    un circuit de détection (78) pour détecter le signal intermédiaire, et générer un signal de détection ayant une valeur de tension correspondant à une quantité de déviation de fréquence ;
    un circuit de jugement de bande (104) pour générer un premier signal de jugement de bande qui exprime si le signal de détection est, ou non, à l'intérieur d'une plage de tension cible qui est établie selon la bande du signal FM de réception souhaité,
    caractérisé en ce que
    le circuit de jugement de bande (104) est adapté pour générer un second signal de jugement de bande qui exprime si le signal de détection est, ou non, à l'intérieur d'une plage de tension étendue qui inclut la plage de tension cible ; et
    un circuit de détection d'interférence adjacente (98) pour déterminer la présence ou l'absence d'interférence depuis un signal adjacent sur le signal FM de réception souhaité sur la base du premier signal de jugement de bande et du second signal de jugement de bande est pourvu.
  2. Syntoniseur FM (50) selon la revendication 1, dans lequel
    le circuit de détection d'interférence adjacente (98) détermine qu'un état dans lequel le signal de détection est uniquement à l'intérieur de la plage de tension étendue, entre la plage de tension cible et la plage de tension étendue, indique la présence d'interférence depuis le signal adjacent ; et détermine qu'un état dans lequel le signal de détection est à l'intérieur de la plage de tension cible indique l'absence d'interférence depuis le signal adjacent.
  3. Syntoniseur FM (50) selon la revendication 1, dans lequel
    le circuit de détection d'interférence adjacente (98) a un comparateur de fenêtre pour délivrer en sortie un signal de résultat de comparaison selon un résultat d'une comparaison entre une paire de valeurs de tension de référence et le signal de détection ; et
    un circuit pour établir en alternance la paire de valeurs de tension de référence du comparateur de fenêtre à une paire de valeurs de tension pour spécifier la plage de tension cible et une paire de valeurs de tension pour spécifier la plage de tension étendue.
  4. Syntoniseur FM (50) selon la revendication 1, dans lequel
    le circuit de détection d'interférence adjacente (98) a un premier comparateur de fenêtre pour délivrer en sortie le premier signal de jugement de bande sur la base d'un résultat d'une comparaison entre une paire de tensions de référence selon la plage de tension cible et le signal de détection ; et
    un second comparateur de fenêtre pour délivrer en sortie le second signal de jugement de bande sur la base d'un résultat d'une comparaison entre une paire de tensions de référence selon la plage de tension étendue et le signal de détection.
EP08015656A 2007-09-04 2008-09-04 Syntoniseur FM Expired - Fee Related EP2034614B1 (fr)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP2007228415 2007-09-04

Publications (3)

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EP2034614A2 EP2034614A2 (fr) 2009-03-11
EP2034614A3 EP2034614A3 (fr) 2009-11-18
EP2034614B1 true EP2034614B1 (fr) 2011-01-26

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EP08015656A Expired - Fee Related EP2034614B1 (fr) 2007-09-04 2008-09-04 Syntoniseur FM

Country Status (5)

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US (1) US8135370B2 (fr)
EP (1) EP2034614B1 (fr)
JP (1) JP2009081839A (fr)
CN (1) CN101383623B (fr)
DE (1) DE602008004708D1 (fr)

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JP5250226B2 (ja) * 2007-09-04 2013-07-31 東京応化工業株式会社 高分子化合物、ポジ型レジスト組成物、およびレジストパターン形成方法
TWI410057B (zh) * 2009-05-05 2013-09-21 Richwave Technology Corp 頻率調變接收機與其接收方法
JP5297877B2 (ja) * 2009-05-07 2013-09-25 セミコンダクター・コンポーネンツ・インダストリーズ・リミテッド・ライアビリティ・カンパニー 受信装置
DE102009029519A1 (de) * 2009-09-16 2011-03-24 Robert Bosch Gmbh Digital-Analog-Wandlerschaltung und Verfahren zur Fehlererkennung
JP2011172188A (ja) * 2010-02-22 2011-09-01 On Semiconductor Trading Ltd ステレオ信号処理回路
DE102010029497B4 (de) * 2010-05-31 2023-03-16 Robert Bosch Gmbh Verfahren zum Erkennen von Fehlern eines AD-Wandlers
JP2012075068A (ja) * 2010-09-30 2012-04-12 On Semiconductor Trading Ltd チューナ
JP5814649B2 (ja) * 2011-06-17 2015-11-17 富士通テン株式会社 受信装置、および、信号処理方法
JP2013038713A (ja) * 2011-08-10 2013-02-21 Semiconductor Components Industries Llc 音声信号処理回路
US8600331B2 (en) * 2012-04-11 2013-12-03 Black Berry Limited Radio receiver with reconfigurable baseband channel filter
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Also Published As

Publication number Publication date
CN101383623A (zh) 2009-03-11
US20090061801A1 (en) 2009-03-05
DE602008004708D1 (de) 2011-03-10
EP2034614A3 (fr) 2009-11-18
CN101383623B (zh) 2012-07-25
JP2009081839A (ja) 2009-04-16
EP2034614A2 (fr) 2009-03-11
US8135370B2 (en) 2012-03-13

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